The use of fluoride to treat dental plaque is well documented. For example, fluoride is often added to community potable water supplies, consumer products such as rinses, gels, foams and, of course, toothpastes in order to reduce dental caries.
Over the years, various fluoride compounds such as sodium fluoride, stannous fluoride or sodium monofluorophosphate have been used to provide the beneficial activity required to reduce, inhibit, control and prevent dental plaque, and consequently, dental cavities, decalcification of tooth enamel. Professional dental practitioners often use fluoride gels and foams to affect a high degree of plaque control and prevention. Fluoride gels, however, have several shortcomings. For example, when gel-type products are applied with a toothbrush, patients often do not brush long enough to allow the fluoride to get into the interproximal and interdental spaces.
Fluoride gels are also applied by dental professionals using dental trays which fit over all of the upper or lower teeth at the same time and allow the gel to directly contact the teeth for periods of one to four minutes and optimize fluoride uptake by the tooth enamel. Although dental trays tend to be more effective than toothbrushes, currently available fluoride gels lack sufficient stability to remain in the oral cavity for the time period required for maximum therapeutic effect. The problem is especially critical when the dental tray with the gel is turned upside down to submerge the lower teeth in the fluoride-containing gel. In these situations, the gel quickly leaves the dental tray and reduces the effectiveness of the fluoride treatment is reduced.
One attempt to address the shortcomings of currently available products is set forth in U.S. Pat. No. 4,770,634. This reference discloses an aerosol, foamable fluoride product which can be dispensed into the trough of a dental tray. The patentees describe the foam as dense, stable and non-flowable. The compositions prepared in accordance with the '634 patent, however, also demonstrate the aforementioned physical stability problems, especially when used in dental trays which are turned upside down to treat the lower teeth. One of the chief drawbacks associated with these fluoride foams is that they are prepared using substantially all water-soluble ingredients. On the one hand, water-soluble and hydrophilic ingredients make preparing fluoride-based foams easy to formulate and which produce sufficient amounts of foam. On the other hand, the physical nature of such foam ingredients dictates that the foams and the foam cell structure will rapidly dissipate in the presence of (aqueous) saliva due to the inherent weak stability of a hydrophilic foam under acidic conditions and will fail to remain in intimate contact with the teeth for one to four minutes.
In the view of the foregoing, there is still a need for improved dental fluoride compositions, especially in the foam-type formulations. The present invention addresses this need.